ELAPLANE and Stuartl first described a chronic respiratory disease in chickens in 1943. Since that time much information has been published on this subject. The name, changed several times, is now most commonly which is quite descriptive. Research has revealed that chicks infected with Mycoplasma gallisepticum are more susceptible to aerosacculitis than uninfected chicks. Chicks infected with this organism, when complicated with other agents, develop serious pathological changes resulting in deaths and, in those that survive, high condemnations when processed. Flocks grown free of this organism apparently do not develop this condition. This experiment was designed to secure some data on a group of chicks hatched from parents free of M. gallisepticum. A Department of Agriculture news release indicated that in May, 1961, 43% of the condemnations in broiler chickens at slaughter were due to aerosacculitis, representing a tremendous loss of chicken meat.